The present invention relates to compositions and methods for delivery of siRNA to specific cells or tissue. More particularly, the present invention relates to compositions and methods for cell type-specific delivery of anti-HIV siRNAs via fusion to an anti-gp120 aptamer.
The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference, and for convenience are referenced in the following text by author and date and are listed alphabetically by author in the appended bibliography.
RNA interference (RNAi) is a process of sequence-specific post-transcriptional gene silencing triggered by small interfering RNAs (siRNA). The silencing is sequence specific and one of the two strands of the siRNA guides the RNA induced silencing complex (RISC) to the complementary target, resulting in cleavage and subsequent destruction of the target RNA (1). RNAi is rapidly becoming one of the methods of choice for gene function studies, and is also being exploited for therapeutic applications (2, 3). The successful therapeutic applications of RNAi are critically dependent upon efficient intracellular delivery of siRNAs (3).
Currently, there are several methods to deliver siRNA in vivo. These can be divided into physical and mechanical methods (hydrodynamic tail vein injections in mice (4-6), electroporation (7-9), ultrasound (10), and the gene gun (11)); local administration (3) (intravenous injection (12), intraperitoneal injection, subcutaneous injection); and chemical methods (cationic lipids (13, 14), polymers (15-20), and peptides (21-24)). However, the delivery efficiency (desired dose), uncontrollable biodistribution and delivery-related toxicitities must be carefully analyzed.
Recently, the cell type-specific delivery of siRNAs has been achieved using aptamer-siRNA chimeras (25). In this system, the aptamer portion mediated binding to the prostate-specific membrane antigen (PSMA), a cell-surface receptor and the siRNAs linked to the aptamer was selectively delivered into PSMA expressing cells resulting in silencing of target transcripts both in cell culture and in vivo following intratumoral delivery. In a similar study (26) a modular streptavidin bridge was used to connect lamin A/C or GAPDH siRNAs to the PSMA aptamer. Consequently, this system induced silencing of the targeted genes only in cells expressing the PSMA receptor.
Thus, it is desired to develop compositions and methods for cell- or tissue-specific delivery of siRNA molecules for treatment.